Bug report

The new Cairo backends do not produce plots

I tried the new Cairo backends, Qt4Cairo, Qt5Cairo, WXCairo, and TkCairo, but neither of them produced plots for me. (Fedora 27, compiled own python 3.6.4 from source, all extra packages installed from pip3).

Code for reproduction

matplotlibrc:

backend      : TkCairo
# all other lines commented out

code:

from matplotlib.pylab import *
plot([0,1])
show()

Actual outcome

Qt4Cairo, Qt5Cairo - frame but no plot, frame not updated
WXCairo, TkCairo - no frame

Just to be sure, GTK3Cairo makes a frame with a plot, all working fine.
Same for Qt5Agg, WXAgg, TkAgg all work as well

Qt4Agg is broken ("ModuleNotFoundError: No module named 'PyQt4'", there seems to be no such module on pip)

So it seems neither Cairo, WX, Tk, QT5 are broken by themselves, but the integration does not work smoothly, at least in my setup. I have no clue how to debug this.

Expected outcome

A plot.

Matplotlib version

• Operating system: Fedora 27
• Matplotlib version: 2.2.0
• Matplotlib backend (see above)
• Python version: 3.6.4
• IPython: 6.2.1

python compiled from source, packages (current) from pip3